I would just like to point out the flaw in your thinking that a second reflective barrier won't help. everything that is above 0 kelvin (so everything!) radiates heat, so the top pad radiates heat, so a second reflective barrier underneath the first will help the top pad retain heat. since the top pad is not as warm as you are, it will not radiate as much heat, but it still will help.
Also, since any real reflector is not perfect, the reflectivity value will be something less than one. this means that some of your body's radiation will get through the first, and even the second reflective barriers, however multiple barriers will also help with this too.
I think any type of inflatable pad user in the winter should bring a foam pad (keeps things drier and you safer). the ridgerest solite weighs less than the solar, and is cheaper, and unless you're doing some serious mileage, its worth the weight to keep you safe. if i was redoing my system, i would use a short solite with my new full size neoair, since i will pretty much always be wearing some sort of inner bootie for winter camping to keep my feet warm. Also, after hearing about some of the mountaineering and ice climbing accidents this year, like echo oak up in the southfork, i think i would just bring my solite short with me on treks and climbs as part of an emergency kit.
i found using my old short neoair (top) and my ridgerest solar (bottom) on top of less than an inch of snow, the snow did not melt out underneath of me after three night of sleeping in the same spot in a snow cave (which was not that efficient due to a large-ish door opening, but was still better than a tent). On a side note, I think next winter, im going to invest in an icebox igloo maker.